On Fri, 22 May 2020 at 13:02, Chris Wilson <ch...@chris-wilson.co.uk> wrote:
>
> Quoting Chris Wilson (2020-05-22 11:42:07)
> > Our __sgt_iter assumes that the scattergather list has at least one
> > element. But during construction we may fail in allocating the first
> > page, and so mark the first element as the terminator. This is
> > unexpected!
> >
> > [22555.524752] RIP: 0010:shmem_get_pages+0x506/0x710 [i915]
> > [22555.524759] Code: 49 8b 2c 24 31 c0 66 89 44 24 40 48 85 ed 0f 84 62 01
> > 00 00 4c 8b 75 00 8b 5d 08 44 8b 7d 0c 48 8b 0d 7e 34 07 e2 49 83 e6 fc
> > <49> 8b 16 41 01 df 48 89 cf 48 89 d0 48 c1 e8 2d 48 85 c9 0f 84 c8
> > [22555.524765] RSP: 0018:ffffc9000053f9d0 EFLAGS: 00010246
> > [22555.524770] RAX: 0000000000000000 RBX: 0000000000000000 RCX:
> > ffff8881ffffa000
> > [22555.524774] RDX: fffffffffffffff4 RSI: ffffffffffffffff RDI:
> > ffffffff821efe00
> > [22555.524778] RBP: ffff8881b099ab00 R08: 0000000000000000 R09:
> > 00000000fffffff4
> > [22555.524782] R10: 0000000000000002 R11: 00000000ffec0a02 R12:
> > ffff8881cd3c8d60
> > [22555.524786] R13: 00000000fffffff4 R14: 0000000000000000 R15:
> > 0000000000000000
> > [22555.524790] FS: 00007f4fbeb9b9c0(0000) GS:ffff8881f8580000(0000)
> > knlGS:0000000000000000
> > [22555.524795] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> > [22555.524799] CR2: 0000000000000000 CR3: 00000001ec7f0004 CR4:
> > 00000000001606e0
> > [22555.524803] Call Trace:
> > [22555.524919] __i915_gem_object_get_pages+0x4f/0x60 [i915]
> >
>
> Fixes: 85d1225ec066 ("drm/i915: Introduce & use new lightweight SGL
> iterators")
> > Signed-off-by: Chris Wilson <ch...@chris-wilson.co.uk>
> > Cc: Matthew Auld <matthew.a...@intel.com>
> > Cc: Tvrtko Ursulin <tvrtko.ursu...@intel.com>
> Cc: <sta...@vger.kernel.org> # v4.8+
Reviewed-by: Matthew Auld <matthew.a...@intel.com>
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